The Swiss aviation authorities have extended a flight ban for commercial air travel into Monday as volcanic ash continues to spread across Europe.
About 20 countries closed their airspace leaving millions of passengers stranded following the eruption of a volcano in Iceland last Wednesday. It is the worst air travel chaos since the 9/11 attacks in the United States nine years ago.
The Federal Civil Aviation Office said given the latest data it had no choice but to close Swiss airspace for safety reasons until Monday 2pm.
The aviation office will re-assess the situation at the beginning of the week, spokesman Daniel Göring told the Swiss News Agency on Sunday.
Travellers are urged to consult airlines and travel agents, and not go to airports until further notice.
Around 80 stranded travellers spent the night in the waiting room at Zurich airport, a spokeswoman said on Monday.
Swiss International Air Lines says it has cancelled all long-haul flights for Monday, while European flights could resume at 8pm at the earliest that day.
On Sunday Swiss called off about 400 flights. The last plane took off from Switzerland’s main airport of Zurich on Friday. More than 1,500 flights have had to be cancelled since.
However, several smaller airports in Germany and France as well as in northern Spain re-opened temporarily on Sunday apparently to take advantage of a gap in the ash cloud.
The shutdown of commercial air travel has led to overcrowded trains in Switzerland despite extra services laid on for international rail links.
Swiss Federal Railways has doubled its services to neighbouring countries, but many rail passengers have been unable to get seats.
Car rentals, taxis and hotels have also recorded massive bookings.
Millions of stranded travellers across Europe face chaos and the International Air Transport Association (Iata) expects little or no improvement in the short term.
Swiss President Doris Leuthard and Foreign Minister Micheline Calmy-Rey had to cancel their visits to Poland and Bosnia-Herzogovina respectively as a result of the closed airspace.
Leuthard was due to attend the funeral of Polish President Lech Kaczynski on Sunday, while Calmy-Rey was expected in Sarajevo on Monday.
However, Environment Minister Moritz Leuenberger said he would travel to Brussels for a meeting with European Union commissioners.
“I will probably take the train on Sunday,” he was quoted as saying in the Sonntag newspaper.
The EU said it was setting up a group to assess the economic impact of the volcanic ash.
The EU transport commissioner will coordinate the response and evaluate the situation according to European Commission President José Manuel Barroso.
Airlines are estimated to be losing $200 million (SFr213 million) a day as a result of the shutdown.
In Switzerland the head of the Federal Civil Aviation Office, Peter Müller, pointed out the consequences of a flight ban at a time when the economy is about to pick up. But he said safety of passengers and airlines was the top priority.
“The longer the situation continues the more difficult it will become for airlines. Of course the ban also has drastic implications for the whole economy,” Müller said.
The plume of volcano ash reached Switzerland on Friday night. Initially it hovered at about an altitude of 6,000 metres and dropped to about 2,000 on Sunday morning.
Experts said it had begun to lose some of its density, but the cloud is not expected to shift significantly until later in the week.
Urs Geiser, swissinfo.ch and agencies
Zurich airport is Switzerland's largest international gateway and hub to Swiss International Air Lines.
Geneva and Basel also operate regular international flights.
Bern and Lugano are mainly regional airports.
Small jagged pieces of rocks, minerals, and volcanic glass the size of sand and silt (less than 2 millimetres (1/12 inch) in diameter) erupted by a volcano are called volcanic ash.
Volcanic ash is not the product of combustion. It is hard, does not dissolve in water, is extremely abrasive and mildly corrosive, and conducts electricity when wet.
Volcanic ash is formed during explosive volcanic eruptions. Explosive eruptions occur when gases dissolved in molten rock (magma) expand and escape violently into the air, and also when water is heated by magma and abruptly flashes into steam.
Expanding gas shreds magma and blasts it into the air, where it solidifies into fragments of volcanic rock and glass.
Once in the air, wind can blow the the tiny ash particles tens to thousands of kilometres away from the volcano.
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